A century ago, an explosion equivalent to 1,000 atomic bombs devastated over 2,000 km2 of forest and incinerated the reindeer of the Indigenous Evenki reindeer herders in central Siberia. Reverberations of the explosion were recorded all over the world. It lit up the skies in London and Paris so brightly that newspapers could be read outside for several nights. But after decades of international research, the mystery of its cause remains unsolved.